Mr. da Silva of the leftist Workers' Party finished with 48.6 percent of Sunday's vote - short of the majority needed to win a second term. His main rival, former Sao Paulo Governor Geraldo Alckmin of the Social Democracy Party, received 41.6 percent support.

The runoff will be held October 29.

During his first term, President da Silva enjoyed wide support and was credited with stabilizing Brazil's economy and anti-poverty social programs. But his popularity slipped in the final days of his re-election campaign, in part because of allegations of corruption within his party. Mr. da Silva was first elected in 2002.

Brazilian voters also elected state governors and members of congress Sunday.